Yamakachi and the Giant Snakes of Japan

Giant Snakes of Japan
by Brent Swancer

Snakes have always instilled a mix of fear and fascination in humans. They play a role in the folklore and legends of cultures all over the world, often represented as being foreboding, evil creatures. Dark and insidious, snakes have haunted us, spawned myths, and slithered through the primal subconscious of mankind since time unremembered

For many people, even a small snake can provoke a fearful reaction or at the very least, unease. The overall largest snake known in terms of weight to length ratio is the green anaconda (Eunectes murinus) of South America ~ two images above ~, which reaches lengths of 6 to 9 meters (19 to 29.5 feet), and weights from 250 kg (551 lbs.) to 500 kg (1,100 lbs.). One recorded green anaconda was 11.4 meters long, and it is thought that there are specimens that occasionally achieve lengths of 10 meters (33 feet).

The reticulated python (Python reticulatus) ~ three photos above ~ of Southeast Asia is commonly regarded as the longest snake, being slightly longer on average than the green anaconda, but not as heavily built. These are both huge snakes to be sure, yet like something out of a nightmare, snakes even larger still have occasionally been reported in the far flung, remote corners of the earth. There are even accounts of true giants, snakes in excess of 40 feet long, sometimes said to be able to attack and kill cattle, and even humans.

Terrifying, monstrous serpents may seem to be strictly denizens of the uninhabited jungles and swamps of the world, creatures to be found in the rainforests and jungles of South America or Africa. However, Japan too has had a history of giant snake accounts.

There have long been stories of pioneers encountering and being frightened by large snakes lurking in the wilds of Japan. Early settlers of mountainous regions would tell of snakes so large that they could devour dogs and there were occasional tales of doomed travelers being attacked by giant snakes. Peasants of some thickly wooded areas also believed in a kind of large boa, which they called the uwaba-mi, or yamakachi. These snakes were rarely seen, but highly feared by locals, and there were circumstantial reports of women, or children being eaten. It was not uncommon for residents of these areas to carry some sort of weapon with them when venturing out alone, in order to ward off any giant snakes they might encounter. Allegedly, these boas were sometimes even captured alive and displayed for money by enterprising villagers.

Accounts of mysterious, large snakes have existed right up to the modern day. Perhaps one of the best known modern cases of giant snakes in Japan comes from Mt. Tsurugi (above), located in Tokushima prefecture. This 6,413 ft peak lies within Tsurugi Quasi- National Park, and is the second highest mountain on the island of Shikoku. Mt. Tsurugi is highly associated with paranormal phenomena, and legend has it that it is a man made pyramid, with some believing that King Solomon’s treasure is located somewhere beneath it. Interestingly, this treasure is supposedly guarded by a colossal snake that will kill any who approach.

It may seem as if this is all surely pure myth, but is it?

On May 26, 1973, forestry workers on Mt. Tsurugi came across a snake that was described as being as thick as a telephone pole, with shiny black scales and a white underbelly. According to the startled workers, 5 meters (around 16.5 feet) of the snake was protruding from thick underbrush, and they estimated that the full length of the animal would have been a whopping 10 meters (33 feet) or more. The snake was reported to emit a loud chirping noise and piping cry before slithering away into the foliage. This report caused widespread panic among residents, and some even reported seeing other snakes in the area that were estimated as being 8 meters (26 feet) to 11 meters (36 feet) long.

The following month, in June 1973, local officials responded to escalating fears by mounting a large scale expedition to try and find the giant snake or snakes. Volunteers scoured the mountainside in the vicinity of the sightings, looking for any evidence at all for what people had reported seeing. They found no snake, but they did discover what appeared to be a track left by the creature. The long track was 40 cm (around 16 inches) across and led through fallen weeds and flattened brush. Those who examined the track said it was undoubtedly that of a large snake of some kind. Bizarrely, a local museum actually claims to have a jawbone measuring 34 cm (13 inches) wide, which is claimed to be from the very same snake. Critics have pointed out that it is merely the jaws of a shark cleverly arranged to resemble a snake’s jaw.

Another mountain, Mt. Tateiwa, in Gunma prefecture, is also said to be inhabited by giant snakes.

Other areas of Japan have had their own modern day giant snake encounters as well. On January 24, 1987, a 7 meter long snake was seen on a poultry farm in Kochi prefecture. The farmer, a Mr. Asakura Kayoko, reported hearing a commotion coming from one of his chicken coops. When he went to investigate, he found what he at first took to be a log inexplicably lying across the top of the coop. Closer inspection revealed it was in fact a huge snake in the process of eating one of his chickens, and apparently had already eaten others. The farmer’s dogs ended up chasing the snake off of the property.

In Izu prefecture, a giant white snake reported as around 9 meters (29.5 feet) long halted construction of a hotel when it appeared out of the surrounding wilderness. Construction workers were so frightened by the snake that they refused to return to work for several days. An inspection of the area turned up nothing.

What were these people seeing? Could the giant snakes seen in Japan represent an unknown endemic species? Although Japan has a range of indigenous snakes, there is no type of boa or python native to the archipelago. Additionally, there is no known indigenous snake that even approaches the sizes being described in these giant snake accounts.

The largest known snake in Japan is the Hime habu (Ovophis okinavensis), a poisonous pit viper of the southern Ryukyu islands, which reaches average lengths of 1.1 to 1.8 meters (3.6 to 6 feet) long, and a maximum of 3 meters (9.8 feet). It seems unlikely that a snake this size could be mistaken for something 8 to 10 meters in length. The Hime Habu is not only too small to account for the sightings, but it is only found in southern islands of Japan, and not in the areas where the giant snake reports originated. If there is indeed an undocumented species of snake responsible for these accounts, then it is a type that has no fossil record or any known precedent in Japan.

In light of the lack of records in Japan for anything like what is described in these giant snake reports, perhaps we have to look at species that have originated from elsewhere. The most likely culprit for the modern accounts seems to be that people are seeing escaped exotic pets and perhaps overestimating the extreme sizes involved. Several types of pythons and boas are widely available in the Japanese pet trade, so an escaped pet is not beyond the realm of possibility. The relative scarcity of current giant snake sightings reports could be due to the rarity of these animals escaping or being released into the wild.

If we are dealing with escaped exotics of some sort, then the reported sizes imply a specimen of truly enormous size. Even for the largest snakes in the world, green anacondas or reticulated pythons, the sizes described in the Japanese giant snake sightings would represent the very upper limits of what these snakes are known to achieve. So we are either looking at truly giant escaped captive specimens, or eyewitnesses are misjudging the sizes. Could we be dealing with escaped exotics that subsequently grew to an enormous size?

Indeed snakes such as pythons and anacondas are thought to be able to reach sizes beyond the current record holders. If left to grow uninterrupted in an ideal environment, certainly we could expect to see one of these snakes achieve the lengths reported in the Japanese cases. However, a snake this large would be old indeed, and would need favorable conditions. Pythons and most types of boa are found typically in humid, tropical environments, which would be quite different from the temperate climate found in most of Japan. These snakes tend to have a low tolerance for extremes of temperature, and do not do particularly well in colder environments. Even in captivity, these species need careful monitoring of the temperature in their environment.

It is quite possible that exotic pythons, most boas, and anacondas, would have a difficult time coping under the environmental conditions in places like Mt. Tsurugi and Izu. Although the Mt. Tsurugi and Kochi sightings occurred in the relatively more humid and warmer summer months, perhaps an escaped exotic would not survive the oncoming winter and thus we are left with isolated reports. Maybe these snakes simply did not survive the cold. The challenge that the Japanese climate would present makes it seem unlikely that an introduced exotic from a tropical habitat would survive long enough to achieve the 8 to 11 meter sizes reported here.

The possible exception to this would be the boa constrictor (Boa constrictor)*, a moderately large, heavy set snake from Central and South America that can reach sizes of around 4 meters (13 ft) and over 100 pounds (45 kg).

Boa constrictors (above and below) have proven to be much less ecologically specialized and thus more flexible than other types of boas, displaying a high degree of versatility in their choice of habitat and high tolerance for temperature fluctuations. As a result, boa constrictors have a massive territory, with a range extending from Mexico all the way down to Argentina. Within their vast range, boa constrictors are found in a wide variety of environmental conditions, inhabiting everywhere from low lying tropical forests to cooler mountain woodlands and even semi-desert conditions. In the extreme limits of their territory, they are even known to hibernate during the coldest months.

This high versatility and tolerance for varying ecological conditions suggests that a boa constrictor could feasibly survive in the conditions of the Japanese wilderness. However, if the 8 to 10 meter long snakes that were seen are indeed boa constrictors, then they would be far larger than the largest known specimens of that species. Even an abnormally large specimen of boa constrictor would be unlikely to achieve such a size. Again, misidentification of size would most likely be involved such reports.

The question remains whether escaped exotics could possibly explain the more historical accounts of giant snakes in the wilderness. It is more difficult to imagine old time pioneers and settlers of new areas coming across imported snakes from other countries.

The idea of giant snakes roving the remote areas of Japan is as bizarre as it is frightening. Are these things real and if so, are they a threat? As of yet there is no real hard evidence to support the claims, yet as long as people continue to see these phantom serpents, there will be those who look to the forests and wonder.

*Boa constrictor is in fact both the common name and the Latin or binomial name. ~ Loren

About Loren Coleman
Loren Coleman is one of the world’s leading cryptozoologists, some say “the” leading. Certainly, he is acknowledged as the current living American researcher and writer who has most popularized cryptozoology in the late 20th and early 21st centuries. Starting his fieldwork and investigations in 1960, after traveling and trekking extensively in pursuit of cryptozoological mysteries, Coleman began writing to share his experiences in 1969. An honorary member of Ivan T. Sanderson’s Society for the Investigation of the Unexplained in the 1970s, Coleman has been bestowed with similar honorary memberships of the North Idaho College Cryptozoology Club in 1983, and in subsequent years, that of the British Columbia Scientific Cryptozoology Club, CryptoSafari International, and other international organizations. He was also a Life Member and Benefactor of the International Society of Cryptozoology (now-defunct). Loren Coleman’s daily blog, as a member of the Cryptomundo Team, served as an ongoing avenue of communication for the ever-growing body of cryptozoo news from 2005 through 2013.

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  1. When dealing with unusual creatures from Japanese legend and folklore, it helps to remember the huge influence of Buddhism, which came from India by way of China. As a result, many of the Japanese monster tales are clearly local versions (perhaps distorted) of either Chinese or Indian monster tales. It’s easy to imagine stories told by Buddhist monks about giant snakes in India or Southeast Asia becoming “local” in the retelling.

    This makes me wonder, though, whether the raiju may also be a legend not originally native to Japan.

    As for the recent snake sightings — who knows? They would be more convincing if the snakes had been captured, which should have been possible and (if they were in fact a safety concern) should have been done.

  2. I’m thinking that if they are exotic pets let loose or escaping, that they probably wouldn’t have survived winter. There are only a handful of snakes that can stand freezing tempertures and survive. Also the all white snake would have to be a Leucistic. Even albinos have some sort of yellow pigmant to them.

  3. “There are even accounts of true giants, snakes in excess of 40 feet long, sometimes said to be able to attack and kill cattle, and even humans. ”

    The existing/known under 30 foot long anacondas and pythons have already attacked and killed humans and cattle.

    If the largest snakes have been 33 feet or so a 40 foot snake would be within the realm of possibilities.

  4. Fhqwhads:
    I see you’re referencing the Nagas,the Mythological Snake deities of India.

    You’re like me—you know “stuff.” :)

    Speaking of Buddhism—in certain legends regarding the Buddha he is “protected” by a Naga. Curioser and curioser…

    You’re right—some of these tales or legends may have their origin in Indian legends making their way to China and Japan. POSSIBLY.

    Personally, though, I have no problem believing snakes 30-plus feet long could exist in Japan or elsewhere. Hopefully more sightings will come.

  5. Cryptoraptor: Large snakes don’t typically live in climates as cold as Japan, probably because basking is not as effective in warming up for large animals. A 40 foot snake in the jungles of Indonesia, maybe; in Japan, not likely.

  6. fhqwhgads- A good deal of these stories in Japan also derive from the old tradition of hyaku monogatari , or “one hundred stories. This was a popular form of entertainment, especially in Edo Japan. It involved groups of people getting together to exchange spooky stories of the strange and unusual, which were known as Kaidan .

    In these gatherings, 100 wicks would be lit, and after each story, one would be extinguished until darkness came, afte which it was said a monster would appear. The main goal of these story tellers was to constantly outdo the last until finally, everyone would get a good scare. The stories could be based on personal experiences, things they had heard, or stuff they plain made up. A lot of the recurring tales were passed on and there were even published compilations of them. This literary form allowed many of these oral traditions to endure. As the tales were told by different people and in different places, the creatures presented would have taken on certain recognizeable traits. Hyaku monogatari was certainly important in the development of folklore and myths in Japan.

    Of course Chinese influence is also quite strong in Japan, so it was a mix of these that helped form Japan’s unique take on some of these legends.

    Although the folklore of China and Buddhism, as well as these stories, have a strong influence, I feel it would be a mistake to use that as a reason to diregard the cryptozoological importance some of this folklore may hold. Shared cultural mythology could just mean that the Japanese used similar ways to express and expolain the same sorts of mysteries. Of course the natural world would be explained through the cultural lens they were familiar with, in this case Chinese myths. I don’t think this is an automatic indicator that all of this is pure fantastical fabrication, although it may be.

    We still have many documented animals that are cloaked with folklore, some of it very similar to the Chinese versions of the same animals. We also have many myths throughout the world that are very similar from culture to culture, for instance hairy men and dragons. If we discount Japanese folklore due to its outside influences, we have to also disregard the obviously important folkloric elements of other cryptids throughout the world.

    There are similar ways to explain the same phenomena, to come to some understanding based on what they know. The Japanese knew the Chinese stories and the Hyaku monogatari stories, and this may have influenced how they saw certain zoological phenomena. I think it is not a reason to ignore them.

    My aim here is to examine the possible zoological connections, if any, that this folklore has. I am a biologist, not a folklorist, yet the folklore intrigues me and I want to understand it in its biological context. I feel this is obviously an important part of cryptozoology when dealing with ethnoknown animals with strong cultural significance.

  7. cryptidsrus: Actually, I was thinking of stories like this (which is much more of the paranormal-monsters type) and of dragons and other items of Chinese culture which the Japanese made their own. But you’re right; the stories about Nagas could lie behind the snake stories. Maybe.

    As I posted before, I think the biggest problem with really big snakes in Japan is the climate. A reptile basking in the sun takes in energy proportional to its area, but the volume of flesh and blood that needs to be warmed is proportional to the reptile’s volume. This makes it harder for a large crocodile or snake to raise its temperature above that of the surroundings than for a small one, which is probably why we find small snakes all over but really large ones only in warm climates.

  8. I grew up outside of Midland Michigan. Way outside actually, real country. Our neighbors had an auto repair shop on their property and the obligatory junk yard behind it. They always claimed that their was a huge snake living back there, but my parents didn’t really believe it. Then my dad actually saw the thing. He said it looked like a common garter snake but was 12 feet long and 6 inches in diameter. He said it appeared to be consuming a rabbit. I’ve since asked him if the story was true and he confirmed it. The neighbors didn’t know where it came from, only that it had been there a long time.

  9. The climate would be a considerable obstacle, but then again, as is often seen, very little is IMpossible when it comes to mother nature. Excuse me, Mother Nature. That brings to mind another cryptid…the Taezulwurm which is supposed to (if memory serves), a lizard like creature living in the Alps in tunnels and caves and holes.

    As for Japan, another obstacle is the population density. Correct me if I’m wrong, but isn’t Japan about as seriously populated as it gets, so to speak? Just how much untamed land is there in Japan? Enough to hide a 30-40-50 foot monster snake?

  10. springheeledjack- This is a common misconception people have of Japan. The population density is very high if you just look at the statistics on paper, but this is misleading. The fact is that around 90% of that population is concentrated in the main metropolitan areas of the coastal plains. This 90% of the population lives on only around roughly 10% of the land area.

    Japan is mostly mountains. The vast majority of Japan is sparsely populated, mountainous terrain, much of it unsuitable for mass settlement. There is actually a good deal of remote, uninhabited land in Japan. As a matter of fact, the rural areas that are inhabited are becoming ever less populated, as census figures for many such areas show a sharp decrease in population as more and more people head to the cities. So even the more isolated areas are becoming increasingly devoid of people.

    All of this means that the image that everyone has of thrumming, neon filled metropolises pulsing with millions of souls is actually comprising only a fraction of the land area in Japan.

    Trust me, I have slogged through the mountains and backwaters of Japan, and as far as the terrain goes, there is more than enough for something to remain hidden.

    I hope this puts things into perspective a little and makes you consider the possibilities.

  11. mystery_man: Yes, probably the majority of the land mass of Japan is low-population. BUT the part that is sparsely populated is (understandably) almost entirely the part where it is too cold to grow rice.

    springheeledjack: The plausibility of giant snakes in cold climates is not much improved by appealing to the Tatzelwurm. You might as well appeal to the Midgard Serpent — you can’t get any bigger, and it was a Norse legend. There is a plausible reason why large reptiles are not found in cold climates, and that reason would really need to be answered by verifiable observations.

    dorksaber: I wonder if the big snake didn’t winter under the repair shop or some other human-occupied building. A heated building could take much of the sting out of a Michigan winter. But medieval Japanese buildings were built to be cool in summer, and they were COLD in the winter.

  12. fhqwhgads- Hey, you’re getting no disagreement from me on that point. I devoted a good portion of this article discussing the challenges that the climate in Japan would face for a snake this large. I’m not sure where you see me disagreeing on that. You are absolutely right, and I tried to illustrate that here.

    That being said I will say that a lot of the sparsely inhabited or remote land is not really extremely cold. A lot of it is just very steep, making it unfavorable for habitation due to landslides and other factors, and much of it is heavily forested or not good for agriculture. There are a lot of cool mountain woodlands that are not reaching a deep freeze or anything in winter. When I was discussing candidates, I brought up the boa constrictor, which does live in some surprisingly temperate climates within the extremes of its native range, and has even been observed to hibernate. While I’m not sure about a native snake getting that large, perhaps something like the boa constrictor could survive in some areas here. Perhaps it was surprising enough to cause size misjudgments.

    The summers in Japan can be quite hot and humid, so an very large exotic of other species may have been able to hang on in those conditions, but the winter probably would have done them in, except in the more moderate zones where a boa might do alright.

    So Japan is temperate, but not all of the forested regions are super cold in winter, especially if you consider the more low lying, temperate woodlands. Too cold for most very large snakes, probably. But I still do want to examine what might account for the stories, especially those settlers of these areas that once took the giant snakes as very real denizens of the forest, and not even particularly imbued with folklore at that.

    As far as snakes using human habitation, I agree, houses in older times would not been much of a help, and it would be hard to imagine a snake that large not being noticed in the small dwellings of the time. It also still would be hard to figure how exotics would be there in the first place. Perhaps escapees from the various misemono sideshows that were once quite popular in Japan. These sideshows often had cabinets of curiosities that included elaborate gaffes as well as live specimens of exotic species. Some of these strange far away animals could have even instigated the tales to begin with.

    As for a body or verification, well, tell me what cryptid isn’t in need of that. That sounds like the age old requirement for not only cryptozoology, but science in general. I’m just presenting the information for everyone to enjoy and come to their own conclusions. I am not trying to argue that these giant snakes are real. I am curious, though, and feel this is a phenomena worth considering.

  13. And one more thing about rice, it requires large, flat areas with intense irrigation, requirements that are hard to meet in the mountainous areas, regardless of temperate.

  14. M_M,

    I have to admit that I had an ulterior motive for writing what I did–I was taking a pot shot at an age old argument against cryptids, which concerns viable space available for a population of cryptids. I’ve heard it used against BF, Nessie, and the like…that there are SO MANY people, that how could a population possibly hide from humanity when we have 6billion+ people on the planet…and so on and so forth.

    As you said, even in Japan, where population density can be staggering, there is still plenty of untamed wilderness for critters (often large) to live undetected.

    Sorry for using you as bait, but I want to stress that point, and it applies across the board for any country.

    People tend toward making their homes in places accessible to all the necessities in life, which usually means cities, and once you step outside those cities, there is plenty of ground (and water) for creatures of size to move through and even take up residence in without being seen very often.

    Fhqwhgads, I just threw the Tatzelwurm for reference of other reptilian cryptids in mountainous and colder regions…you are right, there is no legitimate evidence for it either, but there have been accounts nevertheless…I do agree…finding a 30-50 foot snake up in the colder mountainous areas is rather far fetched, but then again if animals do anything on this planet, it is adapt…and animals have proved time and again, that if there is a niche to fill, animals find a way to do it. And there have been accounts of bigger than average snakes…so who knows…we keep our ears and eyes open and see if anyone else encounters something.

    In the meantime, let’s not be speaking ill of Jörmungandr…

  15. springheeledjack- Well, you got me, I took it hook, line, and sinker!:)

    I’m actually glad you mentioned it. Being someone who investigates and writes about Japanese cryptids and zoological mysteries as much as I do I often come up against that sort of thing, perhaps even more than those dealing with many other cryptids in other regions. Believe me, I’m used to it. People just have very set misconceptions about the amount of untamed land over here, and it is a constant battle to try and illustrate just how the ecology and wilderness in Japan really is rather than how people perceive it through the media or looking at statistics on a piece of paper.

    It is sometimes hard to get this across and it is an argument I’m constantly and sometimes tiresomely faced with.

    So you bringing that up allowed me a chance to yet again underline the fact that Japan is not filled to the brim with people on every square kilometer of land, and that the population is crammed into actually quite a comparably small area.

    So yeah, I bit. No worries. Hey, at least it seems you were already aware of what I was saying. ;)

  16. Yeah, I like to drive that home every chance I get too…it is just a natural way of thinking I would guess…if you see anything in the news on Japan, it almost always centers around the bustling civilization of the city life, and mention of just how short on space everyone is there…SO, most people assume that there is no unpopulated space…for leisure, let alone cryptids.

    It’s an argument that frustrates me whenever I hear it in the states too…I live in Iowa and everyone thinks there’s just endless corn fields. While we do not have the expansive forests of the Pacific Northwest, there is a fair amount of uninhabited ground here too…definitely enough for a larger than average bipedal cryptid to roam through…and probably other things too…just wish we had more deep, scottish type lakes here:)

    So, thanks for the great post–I am always on the watch for cryptids in other countries, and Japan has a lot of history and definitely in a goood place for cryptids…especially the water varieties:)

  17. There has been a reward out for 100yrs for any snake in excess of 10 meters,and as yet it has not been collected.Snake lengths are easily overestimated by people with untrained eyes.This is especially the case where the ‘shock’ of discovery is factored in.I’ve been keeping,catching and breeding snakes for 40yrs so I have an eye for it,but most people would have very little chance of an accurate assessment of a snakes length,especially a large one that gave them a fright.
    As has been pointed out though,there is little possibility of large boids being able to survive the cold winters in Japan,this is why all large constrictors are found in environments that can heat their large bodies year round.Of course if there were giant snakes in Japan,you would obviously come across many smaller individuals,babies,juveniles etc,and alas there are none.
    I will add one thing however(to keep the mystery alive),as Japan is a very volcanic
    country,so I suspect there must be many places underground that stay quite hot even in the depth of winter!

  18. Repost from other giant snake article:

    I live in Japan and I’ve been to two festivals which involve legends of giant snakes.

    This festival on Mt Kurama north of Kyoto dates from the 9th Century when a monk encountered two large snakes. One he killed and the other he spared on the condition to would protect the waters of the mountain. Every year in June they do festival where monks cut at bamboo stalks which represents the snake killed long ago.

    Another festival in Niigata involves 2 giant snakes. A woodcutter encountered a giant snake and killed it. He pickled the meat and told his wife not to eat it till he got back. She did anyway and was transformed into a giant snake herself. She planned at one point to destroy the village but the villagers eventually killed her. The villagers make a long snake of bamboo that they parade through the town.

    I wonder if not today then in the past large anaconda-like snakes might have lived in prehistoric Japan which had a warmer climate. It might have been encountered by the first paleolithic hunters 30,000 years ago downthru Jomon and Yayoi times and the stories of these encounters were passed down thru the generations as the species died out due to over-hunting and climate change.